How to Refresh a Car Battery

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How to Refresh a Car Battery
Test your old battery to determine if reconditioning is an option for you. (bio battery image by dinostock from

The battery in your car has a tough job. It needs to provide service in ice cold winter conditions and also function in the heat of summer. Technology has created a much longer life battery than the vehicle owners of 50 years ago were able to purchase. Modern battery function is, for the most part, very reliable. There are a few things that the owner can do to improve the longevity of his car’s battery. Taking a few preventive maintenance steps will allow the battery to be more easily reconditioned when the time comes.

Skill level:

Things you need

  • Protective eye wear
  • Battery post/terminal cleaner or wire brush
  • Volt meter with probes
  • Screwdriver
  • Battery load tester
  • Battery hydrometer
  • Plastic funnel
  • Electrolyte fluid
  • Battery treatment
  • 6/12-volt trickle battery charger

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  1. 1

    Put on the safety glasses. Place a battery post cleaner on each battery post and twist it back and forth until the posts become bright and shiny. If you do not have access to a battery post cleaner, a wire brush can be used to scrub the film and corrosion off of the posts.

  2. 2

    Check the voltage of your battery by placing the positive probe of your volt meter on the positive battery post and the negative probe on the negative battery post. Any reading less than 12 volts indicates that there is a problem with at least one battery cell.

  3. 3

    Gently pry the cell covers up with a screwdriver. Remove the covers and set them aside. Use extreme care not to splash any battery electrolyte solution onto your skin.

  4. 4

    Test the battery cells. Place the red, positive probe from the volt meter on the positive battery post and the other probe in the first battery cell. If the cell does not read at least two volts on the meter, there is a problem with that cell. Test each cell and read the meter, making a mental note of the readings.

  5. 5

    Perform a load test. Attach the positive lead from the load tester to the positive battery terminal first, and then place the negative lead on to the battery’s negative post. This will prevent sparking. Switch on the load tester and check to see that the load does not drop below 12 volts. If the battery fails the load test, it must be replaced.

  6. 6

    Perform a hydrometer test. Squeeze the bulb of the hydrometer and insert the tube into a battery cell. Note which colour the fluid rises to. Green = The battery is good. White = the battery is fair. Red = the battery is in need of a long and slow charge. Make sure the electrolyte fluid covers the lead in each cell by at least 1/8 inch. Repeat this test to all cells. Replace electrolyte fluid in all low cells. Pour it into the cells slowly with a funnel. Do not overfill the cells.

  7. 7

    Add the battery treatment chemicals (purchased at any good auto parts supplier). Follow the chemical manufacturer's instructions on adding the chemicals. Replace the cell covers and place the battery on a trickle charger for at least 24 hours.

Tips and warnings

  • If you can not tell which battery post is which on your battery, the positive post is always larger than the negative post.
  • Never set a battery on a cement floor as it will ruin the battery. Always place a board underneath the battery to keep it off the ground.

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